Core for pressure-sensitive adhesive tape



Dec. 24, 1963 wjc u 3,115,246

CORE FOR PRESSURE-SENSITIVE ADHESIVE TAPE Filed Sept. 19, 1960 //VVEN70R N mww m W/4 6 Ev w/ 5 IL United States Patent 3,115,246 CQRE FOR PRESSURE-SENSKTIVE ADHEIVE TAPE Leslie G. Wicklund, Falcon Heights, Minn, assignor to Minnesota Mining and Manufacturing Company, St.

Paul, Minn, a corporation of Delaware Filed Sept. 19, 1960, Ser. No. 5609 6 Glairns. (Cl. 20659) This invention relates to annular cores for rolls of normally tacky sheet material, providing an inexpensive core on which pressure-sensitive adhesive tape can be convolutely wound in either a clockwise or a counterclockwise direction and from which all the tape can be removed and used.

Cores for pressure-sensitive adhesive tape are usually made from bulky inexpensive materials which have low cohesive strength but which provide the desired stillness at low cost. A typical manufacturing procedure involves forming a tube by spirally or helically winding from 7 to 40 plies of chipboard, jute paper or the like, on a cylindrical mandrel to a thickness of perhaps /8 inch, an inexpensive adhesive, such as pre-cooked dextrin dissolved in water, being used to bond the plies together. The tube is then sliced at right angles to its axis to form tape cores of the desired width.

Tape cores which are formed as described above suffer from the very great disadvantage that the innermost layer of tape cannot be removed and used, the low strength core disrupting or delaminating and adhering to the pressure-sensitive adhesive. Tape manufacturers have compensated for this unusable material by winding additional amounts of tape on each roll; nevertheless, a customer is likely to feel both irritated and cheated at being unable to use all the tape supplied. Further, in instances where it is desirable to make flying splices (as is frequently the case when high strength filament tape is being employed on high speed machinery), it is almost impossible to employ tape wound on cores of the type just described. Nevertheless, since plastic or metal cores are relatively expensive compared to chipboard and jute paper cores, attempts have been made to modify the latter.

It has been felt that a saturant resin might be employed to unify the outer layers of a paper core and to render its surface releasable from pressure-sensitive adhesive tapes, but this is both expensive and difiicult. It has also been proposed to cover a conventional paper core with a tough, delamination-resistant parchment paper strip, one surface of which has previously been treated to decrease its affinity for pressure-sensitive adhesives, but insofar as I am aware there has heretofore been no commercially feasible way to bond the ends of the treated strip to the core. If the ends are merely abutted and adhered to the underlying weak paper layers, removal of the innermost layer of tape at normal unwind speeds tends to lift one or both of the ends and disrupt or delaminate the core, thereby ruining at least some of the tape. Most release coatings used on the outer surface of the parchment strip to render it releasable from pressure-sensitive adhesive tapes also prevent the formation of firm bonds with adhesives or glues normally used in tape core construction.

, As a result, if one end of a parchment strip, coated with a release agent and adhered to a paper core, is lapped over the other end of the strip and adhered thereto, the innermost layer of tape can be removed only when the direction of removal is in the same direction as the outer end of the parchment strip extends; when the tape is so wound that it is removed in the opposite direction, failure occurs in the same way as when both ends of the strip are adhered directly to the paper core. Since it is not feasible in commercial practice to align tape cores so that the tape is always applied in the same direction, this solution has proved only 50% effective.

I have now devised a novel tape core on which pressuresensitive adhesive tape can be wound in either direction and thereafter removed at normal unwind speeds and used in its entirety. In accordance with a preferred embodiment of my invention, at least one of the outermost plies of chipboard or jute paper used in making a conventional core is replaced with a narrow strip of tough delarninationresistant sheet material, which is helically wound on the underlying paper tape body so as to leave a major peripheral portion of the body exposed. A conventional inexpensive core adhesive is preferably used to bond this strip in place. Thereafter, a wider strip of tough delamination-resistant sheet material, having a surface to which normally tacky and pressure-sensitive adhesive tapes may be adhered and subsequently removed, is helically wound over the exposed body and the first strip and similarly adhered thereto so as to constitute substantially the entire periphery of the so-for med tube, the edges of the wider strip being abuttingly juxtaposed over the first strip. The tube is then cut into cores of suitable width, on which tape is thereafter wound in either direction.

My invention will be better understood upon reference to the accompanying drawing, in which like numbers refer to like parts in the several views, and in which:

FIGURE 1 is a view in perspective of a tube as just described, in process of manufacture;

FIGURE 2 is a view in perspective of a single core as taken from the tube of FIGURE 1; and

FIGURE 3 is a side view of the tape core shown in FIGURE 2 with pressure-sensitive adhesive tape wound thereon.

In the drawings, tube 10 comprises annular body I l, which is formed from helically wound plies of chipboard, jute paper, or the like, an inexpensive adhesive being applied to each ply and used to bond the assembly together. Helically wound about annular body 11, and firmly bonded thereto, is a narrow strip 12 of tough, delaminationresistant parchmentized paper, e.g., 40-lb. whalehide, obtained from Kalamazoo Vegetable Parchment Company. Overlying both body 11 and strip 12, and firmly bonded thereto so as to constitute substantially the entire periphery of the tube is a wider strip 13 of supercalenclered parchmentized paper, similar in composition to strip 12 but having a low adhesion coating on its outer or exposed surface 16 and helically wound in such a fashion that its edges 14 and 15 are abuttingly juxtaposed over the approximate midpoint of strip 12. Suitable low adhesion coatings, conventionally used for tape backsizes, include polyvinyl carbamate polymers made by reacting together polyvinyl alcohol and, e.g., octadecyl isocyanate, as disclosed in Dahlquist, Hendricks, and Sohl US. Patent 2,532,011; copolymers of acrylic acids or methacrylic acids with higher alkyl acrylates or methacrylates, as disclosed in Hendricks US. Patent 2,607,711; and copolymers of higher alkyl vinyl esters or ethers and maleic acid or its half esters or half amides, as disclosed in Dahlquist, Ahlbrecht, and Dixon U.S. Patent 2,876,894. Low adhesion materials of these types may be dissolved in volatile organic solvents and applied to one surface of supercalendered parchmentized paper by simple coating procedures, after which the solvent is evaporated to leave a dried deposition product of about one pound per 5,000 square yards of paper; the technique is directly comparable to that described in the cited patents. Other suitable release agents or low adhesion coatings, some of which may be dispersed in Water, will readily occur to persons skilled in the art.

In the manufacture of tape cores having an inner diameter of 3 inches and a wall thickness of about /s inch, I have found that strip 12 may be formed from inch wide material and strip 13 from 4 W inch wide material when the winding is carried out at an angle of approximately 63 to the axis of tube it).

After tube has been formed, it is sliced into short segments at 90 to the axis of the tube, thereby forming cores, one of which is illustrated in FIGURE 2. Core 20 comprises annular body portion 21, narrow parchment'ized paper strip 22, and supercalendered parchmentized paper 23, the last named being externally supplied with lowadhesion-backsize coating 26 and being so positioned that its ends 2- and are abuttingly juxtaposed over approximately the midpoint of strip 22. A roll 3% of pressuresensitive adhesive tape, illustrated in FEGURE 3, is formed by winding about core in an elongate piece of pressuresensitive adhesive tape 31, the tape being convolutely wound with its adhesive-coated surface toward the core. Because of the novel construction of tape core 20, tape 31 can be wound thereabout in either a clockwise or counterclockwise direction, it being equally easy to remove the tape in each case. Edges 24 and 25 and the portions immediately adjacent thereto are firmly adhered to strip 22, which in turn is firmly adhered to the body 21. Since the afiinity of both the radially outer and radially inner surfaces of strip 22 and the radially inner surface of strip 23 for the core-forming adhesives is substantially greater than the aflinlity of the treated radially outer surface of strip 23 for tacky pressure-sensitive adhesive, the adhesion of strip 23 to strip 22 substantially exceeds the adhesion of tape 31 to strip 23. Low adhesion coating 26 makes it possible to remove tape from the core with substantially no more force than is required to separate layers of the same tape convolutely wound upon itself. Tape 31 may be removed in its entirety, without lifting either end 24 or 25, and used in whatever manner the customer desires.

Although I have described herein a preferred embodiment of my invention, it will be readily apparent that a number of changes may be made without departing from the spirit of what I have taught. Thus, although it would be more expensive to do so, strip 12 may cover the entire paper core 1 1, so as to leave no spaces between adjacent edges. Likewise, although supercalendered parchmentized paper which has been provided with a low adhesion coating on one surface is at the present time economically attractive for use as strip 13, metal foils or films of more expensive materials and which are strong enough to resist tearing or delamination, e.g., polypropylene or polyvinyl chloride, may be made to function satisfactorily. Polyethylene which has been subjected on one surface to flame, electrical discharge, or oxidizing acids is more readily adhered to by the dextrin or other adhesive of the type used in paper core construction than is untreated polyethylene. In this structure also the affinity of the inner surface of strip 13 for the core-building adhesive contacting it should exceed the affinity of the outer surface for tacky pressure-sensitive tape adhesives. The calendering of strip 13 provides a smooth surface closely resembling the non-adhesive surface of film-backed tapes. If the backing of the tape to be Wound on cores of the type I have described is itself somewhat rough (as is the case with crepe paper masking tapes and the like), or if the tape adhesive used is relatively hard, it is unnecessary, and perhaps even undesirable, to calender the parchmentized paper backing. In fact, non-woven mats or cloth of various types may be successfully used in such cases. The governing considerations are cost and the desirability of having the surface of the core resemble as closely as possible the back surface of the tape, so that the smoothness of the adhesive surface contacting the core, and therewith the general adhesive characteristics of tr e tape, is substantially he same as the smoothness of the adhesive surface contacting the tape backing in the rest of the roll.

Having described my invention, what I claim is as follows:

1. An annular core for a roll of pressure-sensitive ad hesive tape, said core having a peripheral surface on which pressure-sensitive adhesive tape can be wound in either a clockwise or counterclockwise direction and from which said tape can be subsequently removed at normal speeds without disrupting or delaminating the core, said core comprising a bulky rigid annular body having low cohesive strength, said annular body having firmly adhered to the the radially outer surface thereof a first strip of thin tough sheet material, and overlying and firmly adbored to said first strip so as to constitute substantially the entire periphery of said core a second strip of thin tough delamination-resistant sheet material, the ends of said second strip being abuttingly jaxtaposed and positioned over said first strip, the adhesion of said second strip to said first strip substantially exceeding the adhesion which normally tacky and pressure-sensitive adhesive tape has for the outer surface of said second strip, whereby the exposed surface of said second strip is rendered capable of having aggressive pressure-sensitive adhesive tape adhered thereto and subsequently readily removed without substantial change in the adhesive characteristics of the tape and without lifting the ends of said second strip.

2. The annular core of claim 1 in which the first strip is parchmentized paper, and the second strip is parchmentized paper which has been provided with a low adhesion coating on its exposed surface.

3. The annular core of claim 1 in which the bulky rigid annual body is relatively weak and formed from multiple plies of chipboard.

4. A roll of tape comprising an elongated piece of pressure-sensitive adhesive sheet material convolutely wound, adhesive side in, on a core and completely removable therefrom at normal speeds so that the lap nearest the core displays substantially the same adhesive characteristics as the remainder of the piece, said core comprising in combination an annular readily delaminable body having firmly adhered to the radially outer surface thereof a first strip of tough delamination-resistant sheet material, and a second strip of tough delamination-resistant sheet material firmly adhered to all underlying por tions so as to constitute substantially the entire periphery of said core, at least the ends of said second strip being abuttingly juxtaposed and firmly adhered to said first strip, the adhesion of said second strip to said first strip substantially exceeding the adhesion of said tape to said second strip.

5. A tube from which a plurality of annular cores for pressure-sensitive adhesive tape may be sliced, said cores having a peripheral surface on which pressure-sensitive adhesive tape can be wound in either a clockwise or counterclockwise direction and subsequently entirely removed without either disrupting the core or substantially affecting the adhesive characteristics of the tape, said tube comprising a bulky rigid tubular body having low cohesive strength, a narrow first strip of tough delaminationresistant sheet material spirally wound on and firmly adhered to said body so as to cover only a minor fraction of the periphery thereof, a strip of tough, delamination-resistant sheet material which is wider than said first strip spirally Wound on and firmly adhered to said first strip and the exposed periphery of said body so as to constitute substantially the entire periphery of said tube, said second strip being abuttingly juxtaposed along its lateral edges so that the entire line of abutment is p0- sitioned over said first strip, the exposed surface of said second strip being such that pressure-sensitive tape Wound thereon may be removed therefrom at normal rates with substantially no more force than that required to separate layers of the same tape convolutely Wound on itself.

6. An annular core for a roll of pressure-sensitive adhesive tape formed by slicing the tube of claim 5 at right angles to its axis.

References Cited in the file of this patent UNITED STATES PATENTS Hurlbut Dec. 2, 1890 Freydberg June 5, 1923 Strovink May 7, 1940 Sehieman July 18, 1944 Husson Jan. 9, 1951 Stahl May 5, 1953 Engberg et a1 Sept. 8, 1953 Kaplan Apr. 27, 1954 Dunlap et al June 26, 1956 Holtz Nov. 24, 1959 Rehklau Apr. 17, 1962 

4. A ROLL OF TAPE COMPRISING AN ELONGATED PIECE OF PRESSURE-SENSITIVE ADHESIVE SHEET MATERIAL CONVOLUTELY WOUND, ADHESIVE SIDE IN, ON A CORE AND COMPLETELY REMOVABLE THEREFROM AT NORMAL SPEEDS SO THAT THE LAP NEAREST THE CORE DISPLAYS SUBSTANTIALLY THE SAME ADHESIVE CHARACTERISTICS AS THE REMAINDER OF THE PIECE, SAID CORE COMPRISING IN COMBINATION AN ANNULAR READILY DELAMINABLE BODY HAVING FIRMLY ADHERED TO THE RADIALLY OUTER SURFACE THEREOF A FIRST STRIP OF TOUGH DELAMINATION-RESISTANT SHEET 